The Dictionary of Human Geography

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(seefunctionalism;structural function-

alism). Some have a clear, separate existence

and function – as with a central heating

system – but many geographical studies

involve the pragmatic isolation (orabstrac-

tion) of linked parts from a larger whole (such

as ametropolitan area): where such abstrac-

tions are somewhat arbitrary, the system stud-

ied may yield few valuable conclusions (and be

categorized as a chaotic conception).

Systems analysisinvolves four main decisions

regarding the object of study:

. Whether it is to be conceptualized as open or
closed. A closed system has no links to a
surrounding environment – either as a
source of energy (as inecosystems)oras
a receptacle for by-products of its oper-
ation (as inpollution): an open system
(which is by far the commonest condition)
interacts with its milieu.
. Whether it can be divided into subsystems,com-
prising separate clusters of interdependent
elements weakly linked to each other.
. Whether the links involve flows and causal
relationships, or are presented as black boxes.
Systems of flows involve the movement of
materials, ideas and people (as intrade,
migrationandcommuting); causal sys-

tems involve links that transmit clearly

defined consequences (as inAgenerates

B; e.g. assuming constant demand, an

increase in the supply of a good leads to

a reduction in its price): a black box

incorporates links that may be causal, but

for which the processes involved are not

understood.

. Whether the system involves feedback,
either positive or negative.

The concept of a system and the formal

protocols of systems analysis (many of them

derived from engineering) were introduced to

geographyduring itsquantitative revolu-

tion, and were seen by some as providing both

substantive and methodological links between

humanandphysical geography(see also

ecology;general systems theory;human

ecology;political ecology). More gener-

ally, the concept of a system is applied descrip-

tively in a wide range of contexts to refer to

sets of interdependent phenomena, without

adopting any of the more formal concepts

associated with systems analysis. rj

Suggested reading

Bennett and Chorley (1978); Huggett (1980);

Wilson (2000).

Gregory / The Dictionary of Human Geography 9781405132879_4_S Final Proof page 740 1.4.2009 3:23pm

SYSTEM